Systems have been developed that use image sensors such as CMOS (Complementary Metal Oxide Semiconductor) sensors, and infrared laser sensors, and as this kind of system, there are electronic blackboard system in which an indicated position, that is indicated by having a finger etc. touch the projection surface of the projector, is recognized; and in which the projector projects an image based on the recognition result.
In such an electronic blackboard system, an infrared laser device is arranged on, e.g., the outer peripheral portion of a screen which is a projection surface of a projector, such that infrared laser light emitted from the device is propagated along a plane parallel to the screen. When the infrared laser light is shielded by a shielding object such as a finger, the infrared laser light reflected by the shielding object is detected by an image sensor, and the indicated position is recognized on the basis of the detection result (see Patent Literature 1).
Some infrared laser devices for electronic blackboard systems are each provided with a laser light source and a propagation control mechanism that scans or diffuses infrared laser light emitted from the laser light source. In such an infrared laser device, a propagation region in which infrared laser light is propagated can be changed by changing the scan angle or the diffusion angle of the infrared laser light. In the above electronic blackboard in which infrared laser light reflected by a shielding object is detected, a recognizable region in which an indicated position can be recognized can be adjusted by changing the propagation region of the infrared laser light.